Cam control is the most widespread solution in mechanical chronograph history, not the most sophisticated. It works like this: two or three cams — eccentric profiles fitted on shafts integral to the pushers — rotate with each press and move levers that engage, stop, or reset the chronograph train. No toothed wheel with columns, no progressive selection: the geometry of the cam itself determines the action.
The classic counterpoint is the column wheel system. The column wheel divides its circumference into alternating high and low sectors; each press advances the wheel by one step, and the levers fall into the gaps or climb onto the columns with millimeter precision. The result is a noticeably smoother start and stop at the wrist. The cam system, on the other hand, tends to give a slightly snappier feel, but is less sensitive to dirt, temperature, and assembly tolerances: this is why it was found in movements destined for professional and military use.
The Valjoux 7750 — the backbone of half the Swiss industry since the Seventies — is the immediate reference point. The same goes for Omega's caliber 1861, which has equipped the Speedmaster Professional for decades without anyone ever questioning its reliability in extreme conditions. Sellita SW510, Hamilton H-51-Si, ETA derivatives on an industrial scale: all cam-operated. It is not a compromise choice. It is a deliberate engineering choice when the requirement is robustness over the long term on a large production scale.
The distinction between integrated cam-operated and modular cam-operated matters as much as the distinction with the column wheel. In the modular system, the chronograph mechanism is a package added on top of a base movement; the cams operate in this additional layer. In the integrated system — as in the RW5030 caliber mentioned in the technical literature, or in the original Valjoux movements — cams and chronograph train share the main bridge. The integrated version is flatter, mechanically more rigid, harder to repair without disassembling the entire movement.
From the workbench: a well-regulated cam chronograph is recognized upon reassembly because the pushers oppose uniform and crisp resistance. If you feel a soft step and then a hard one on the same pusher, there is a worn cam or a fatigued return spring. The column wheel has different defects and is often more expensive to correct.